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Laporan Daya Dukung Pondasi
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Daya Dukung (Bearing Capacity)
SIVA1
batuan (rock)
Tanah
kuat
Pondasi Dangkal
~ untuk melimpahkan beban ke lapisan di bawahnya~ utamanya untuk tanah kuat atau beban ringan
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batuan (rock)
Tanah
kuat
Footing PerformanceFooting Performance
Vertical LoadVertical LoadV
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t
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c
a
l
m
o
v
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m
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V
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ElasticElastic
PlasticPlasticmaximum tolerablemaximum tolerablesettlementsettlement
maximum servicemaximum serviceloadload
ultimateultimatecapacitycapacity
safe loadsafe load
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V
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V
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PlasticPlastic
PlungingPlungingFailureFailure
Serviceability Limit StateServiceability Limit State
settlementsettlement
Ultimate Limit StateUltimate Limit State
Maximum allowable load =Maximum allowable load =min min [[safe load, max service load safe load, max service load ]]
Limit States
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ServiceabilityServiceabilityServiceabilityServiceability UltimateUltimateUltimateUltimate
Bearing Pressure DefinitionsBearing Pressure Definitions
FFFF Plan Area, APlan Area, A
Bearing PressureBearing Pressure qqbb == F / AF / ASafeSafe qqss = = .q.quu / / AllowableAllowable qqaa < q< qss (settlement)(settlement)
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FFFF Plan Area, APlan Area, A
Ultimate Bearing CapacityUltimate Bearing Capacity qquu == FFfailfail / A/ A
Foundation FailureFoundation Failure
ForceForceRotational FailureRotational Failure
SIVA Copyright 2001Soil HeaveSoil Heave ResistanceResistance
Pola Keruntuhan
General Failure
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Local Shear Failure
Punching Shear Failure
General Failure
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Local Shear Failure
Punching Shear Failure
FOUNDATION FAILURE1.Generalized Shear FailureFOUNDATION FAILURE1.Generalized Shear Failure
Soil FailureSoil Failure
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Soil FailureSoil FailureLinesLines
rigidrigidradialradialshearshear
passivepassive
log spirallog spiral
SettlementSettlement
2. Local Shear Failure2. Local Shear Failure
minor surfaceminor surface
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Medium denseMedium denseor firm soilsor firm soils
minor surfaceminor surfaceheave onlyheave only
SettlementSettlement
3. Punching Shear Failure3. Punching Shear Failure
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Loose orLoose orSoft SoilsSoft Soils
No surfaceNo surfaceheaveheave SettlementSettlement
Perhitungan Daya Dukung
Untuk menghitung daya dukung dapat dilakukan dengan analisisis berdasarkan :
Data Uji Laboratorium:Teori TerzaghiTeori Meyerhof
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Teori MeyerhofTeori Brinch HansenTeori Vesic
Data Uji Lapangan :Plate Bearing TestCone Penetration Test/CPT (SondirStandard Penetration Test/SPT
Aplikasi Teori Daya Dukung
KEMIRINGAN TERZAGHI MEYERHOF HANSEN VESIC
BEBAN 0
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MUKA TANAH
0 0
DASAR PONDASI
0 0
Daya Dukung Terzaghi
Anggapan-anggapan:1. Tanah homogen isotropik2. Mode keruntuhan pondasi adalah
adalah general shear failure3. Pondasi adalah strip dengan permukaan bawah kasar4. Bidang keruntuhan geser diatas permukaan tanah diabaikan
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permukaan tanah diabaikan5. Permukaan tanah adalah horizontal6. Tidak terdapat gaya horizontal,
momen dan eksentrisitas7. Pondasi terletak pada kedalaman D
Keseimbangan Gaya
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Keseimbangan gaya-gaya yang bekeja pada baji tanah (soil wedge) adalah:
Qu.(2b).1 = - W + 2.Csin + 2.Pp
1 212
= + +f c qq cN DN B N
Strip footing
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1 212
= + +f c qq cN DN B N
Faktor Daya Dukung Tanah Menurut Terzaghidan Berbagai Nilai N yang Berbeda
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Terzaghi Bearing EquationTerzaghi Bearing Equation
applies to strip footing Nc, Nq and N are functions of , and are
usually given in graphical form
qqu nettu nett = c.N= c.Nc c + p'+ p'o o ((NNqq -- 1) + 0.51) + 0.5BB'N'N
SIVA Copyright 2001
usually given in graphical form c, and ' refer to soil properties in the failure
zone below the footing p'o is the effective overburden pressure at the
founding level shear strength contribution above footing level
is ignored : conservative for deeper footings
Terzaghi Bearing EquationTerzaghi Bearing Equation
qqu nettu nett = c.N= c.Nc c + p'+ p'o o ((NNqq -- 1) + 0.51) + 0.5BB'N'N
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Bp'p'o o = = ''oo DD
Generalized soil strength : c, Generalized soil strength : c, (drainage as applicable)(drainage as applicable)
Soil unit weight : Soil unit weight : '' (total or(total oreffective as applicable)effective as applicable)
Overburden
Failure Zone (depth 2B)
Adopt weighted average values !Adopt weighted average values !
Bearing Capacity Factors
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Faktor daya dukung Terzaghi
pi
aN
ea
q
tg
)45(cos2 22
)24
3(
+=
=
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tgNNjikaN
ctgNN
q
c
qc
).1(20:7,5
).1()
245(cos2 2
+=
==
=
+
Faktor daya dukung Terzaghi
pi
ctgNN
tgeN
qc
tgq
).1()
245(2.
=
+=
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tgNNjikaN
ctgNN
q
c
qc
).1(20:7,5
).1(
+=
==
=
Faktor Daya Dukung
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Bearing capacity factors
Rumus Umum Daya Dukung
Secara umum daya dukung dapat ditulis sbb:
qu = c.c Nc + q. D.Nq + .0,5 B.N
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qu = c.c Nc + q. D.Nq + .0,5 B.Ndimana:
c, q, = faktor koreksi yang tergantung pada bentuk,kedalaman,kemiringan: beban, muka tanah, dasar pondasi
Faktor Daya DukungFaktor Daya Dukung
10001000
100100
B
e
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r
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n
g
C
a
p
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c
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y
F
a
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o
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B
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C
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p
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y
F
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NcNcNqNq
NNqq = 33= 33NN
NN = 250= 250
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1010
11
0.10.100 1010 2020 3030 4040 5050
B
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C
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p
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F
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B
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C
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p
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F
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o
r
Friction Angle (deg)Friction Angle (deg)
1414oo
NNcc = 10= 10
3535oo 4646oo
Persamaan Daya Dukung MeyerhofPersamaan Daya Dukung Meyerhof
qquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = = cc.N.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BBNNssddiiqquu = c.N= c.Nccssccddcciicc + + qq.N.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.= c.NNccssccddcciicc + q.+ q.NNqqssqqddqqiiqq + 0.5+ 0.5BBNNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddii
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cc
soil density, soil density, , , ((kN/mkN/m33))BB
DDff q = q = .D.Dff
Bearing Capacity Factors for soilBearing Capacity Factors for soilcohesion, surcharge and weightcohesion, surcharge and weight
functions of friction angle, functions of friction angle, determine by equation or from graphdetermine by equation or from graph
Correction factors for footing shape Correction factors for footing shape ((ss)),,footing depth footing depth ((dd) ) and load inclination and load inclination ((i i ).).
determine from appropriate equationsdetermine from appropriate equations
Faktor daya dukung Meyerhof
).1()
245(2.
pi
ctgNN
tgeN
qc
tgq
=
+=
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).4,1().1(0:14,5
).1(
tgNNjikaN
ctgNN
q
c
qc
=
==
=
Faktor daya dukung Hansen
pi
ctgNN
tgeN
qc
tgq
).1()
245(2.
=
+=
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tgNNjikaN
ctgNN
q
c
qc
).1(5,10:14,5
).1(
=
==
=
Faktor daya dukung Vesic
pi
ctgNN
tgeN
qc
tgq
).1()
245(2.
=
+=
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tgNNjikaN
ctgNN
q
c
qc
).1(20:14,5
).1(
=
==
=
Pengaruh Muka air
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Pondasi dengan Beban MomenPondasi dengan Beban Momen
P
M
eP
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e
e = MPekivalen eksentrisitas beban
Cara Meyerhof menentukan eksentrisitas beban
Cara Meyerhof menentukan eksentrisitas beban
ee
L
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PP
ee
2e LL' = LL-- 22ee
B
Eksentrisitas 2 arahEksentrisitas 2 arah
ee11
LL
22ee22
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PP
ee11
22ee11 LL' = LL-- 22ee11
BB ee2 2
B B
'
=
B B
- -
2 2
e e
2 2
Daya Dukung Berdasar Data Uji Lapangan (In Situ Test)
Plate Bearing Test (Uji Pembebanan Pelat)Standard Penetration Test (SPT)
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Standard Penetration Test (SPT) Cone Penetration Test/CPT
(Sondir)
Plate Load Tests
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Plate Bearing Test(Uji Pembebanan Pelat)
Tanah dengan kekuatan konstanB < 4 Bp
Tanah Dengan Kekuatan Meningkat puu qq ,=
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Tanah Dengan Kekuatan Meningkat Secara Linear Thd Kedalaman
B < 4 Bp Ekstrapolasi Hasil Uji Penurunan
Terzaghi & Peck.
ppuu B
Bqq,
=
iqq 5,11
=
Standard Penetration Test (SPT)
PONDASI TELAPAK (FOOTING)MEYERHOF (1956,1974)
Dimana :qa,1 = daya dukung ijin utk penurunan 1 inchi
dn
a KFNqftB
11,4 =
23
21,4
+=>
BFB
FNqftB na
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qa,1 = daya dukung ijin utk penurunan 1 inchiKd = 1+0,33 D/B1,33Nn = SPT yang dikoreksiF = faktor tergantung energi pukulan SPT
PONDASI PELAT (MAT/RAFT)d
na KF
Nq3
1, =
1,aa qq =
Cone Penetration Test/CPT(Sondir)
SCHMERTMANN (1978) DAYA DUKUNG BATAS PADA TANAH NON
KOHESIF
MENERUS : qu = 28 0,0052(300-qc)1,5
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u c
BUJUR SANGKAR : qu = 48 0,0090(300-qc)1,5 DAYA DUKUNG BATAS PADA TANAH KOHESIF
MENERUS : qu = 2 + 0,28 qcBUJUR SANGKAR : qu = 5 + 0,34 qc
qu dan qc dalam tsf atau kg/cm2
Belajar
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